Magnetic core



NOV. 22, 1960 J, c, EN R ETAL 2,961,624

MAGNETIC CORE 2 Sheets-Sheet 1 Original Filed Dec. 10, 1956 INVENTORJ 944444 f.- B

ATTOR/VAVJ Nov. 22, 1960 J. c. BENDER ETAL 2,961,524

MAGNETIC CORE Original Filed Dec. 10, 1956 2 Sheets-Sheet 2 Cu//e/7 M W/Mr/ef INVENTORJ' BY JAMAM United States Patent MAGNETEC CORE John Carlos Bender and Cullen .l. McWhorter, Houston, Tex, assignors to Houston Oil Material Company, 1136., Houston, Tex., a corporation of Delaware Original application Dec, Iii, 1956, Ser. No. 627,324. Divided and this application May 1, 1958, Ser. No, 736,433

2 Claims. (Cl. 336-192) The present invention relates to a magnetic core and particularly one which is used as a core to carry a winding for use in well bores.

The use of a material, for example, a ferro-magnetic material, which has the property of being magnetic and also a good insulator, is desirable for use as a core to carry the winding of a coil, especially for use in well bores to determine the location of a stuck point of the pipe in the bore or to locate casing collars as well as other elements in the well bore.

Heretofore, such cores have been formed of extruded ferrite or other ferro-magnetic material such as that manufactured by the Henry Crowley Company of West Orange, New Jersey, known as Croloy 20, and good results were obtained when these cores were in good condition. Unfortunately, these cores, as well as others, are very fragile, and after being subjected to conditions in a well bore, for example extreme external pressure due to hydrostatic pressure and the like, these cores crack, break, have holes and spaces between the coil core and adjacent members and become unsatisfactory for use. In quite a few instances, these cores can be used only for one or two runs and then must be discarded.

In some coil assemblies, the coil rod is screwed directly into the top and bottom subs. In this case, the coil lead wire must be brought out through, and insulated from, the coil rod. This is a disadvantage because the coil rod is weakened and in many cases hydrostatic pressure in the well bore shears the insulation and floods the inside of the coil rod thus rendering it inoperative. Also, in conventional coil assemblies for use in well bores, the extreme hydrostatic pressures encountered shear or break loose vulnerable electrical connections and the coil core cannot successfully withstand the shock, bending, torsion and extreme compressive forces to which it is subjected in use.

It would therefore be highly advantageous, and it is an object of this invention to provide a core which not only serves the function of a core for a coil winding, but is a structural element which is rugged and durable and can successfully withstand the shock, bending, torsion and extreme compressive forces to which it is subjected in use.

Still a further object of this invention is the provision of a core for a coil winding which has either conductive or non-conductive magnetic and insulating properties which effectively withstands conditions in a well bore.

It is still a further object of this invention to provide a coil assembly having its core support rod insulated from the connectors at each end and in which the support rod is connected at each end through the medium of insulators in such a manner that the normal tensile strength of the connecting area on the rod is not lessened.

It is yet a further object of this invention to provide a coil assembly having a core formed of a tough, hard and strong resin impregnated with magnetic particles.

Still a further object of this invention is the provision Patented Nov. 22, 1960 of a coil assembly in which there are no vulnerable electrical connections, and in which the coil lead wire is not brought out through the core support rod.

Other and further objects, features and advantages will be apparent from the following description of a presentlypreferred example of the invention, given for the purpose of disclosure and taken in conjunction with the accompanying drawings, where like character references designate like parts throughout the several views, and where Figure 1 is a side elevation, in section, illustrating a step in making a core according to the invention,

Figure 2 is a view similar to Figure 1 and illustrates the next step in making a core according to the invention, and

Figure 3 is a side elevation, in section, illustrating a completed core assembly with a winding according to the invention.

Referring now to the drawings, and particularly to Figure l, a generally tubular core rod support 10 is provided which has the reduced-diameter threaded portions 12 and 14 at each end on which are threaded the insulators 16 and 18, respectively, having the internally-threaded portions 29 and 22, respectively, for this purpose. The insulators 16 and 13 have the externally-threaded pin type portions 24 and 26 so that the core structure can be threaded to other elements in use. The rod 10 is formed of a material capable of conducting electrical energy and the insulators are formed of nonconducting materials. The passage 11 through the core support rod 10 is for the purpose of permitting additional electrical connections below, for example in deto-nating an explosive for impacting a connection to assist in its release. The passage 11, of course, may be omitted if desired.

The insulating connectors 16 and 18 are conformed to fit snugly about the ends of the core support It) and have the outwardly facing shoulders 28 and St) for smoothly receiving the boxes 29 and 31 of adjacent elements when assembled, see Figure 3. Turning again to Figure 1, the inner portion of the connectors 16 and 18 have a diameter portion 32 and 34, respectively, for reception of the sleeve 36 and for providing an annular space therebetween for a reason apparent later.

In constructing the core, the bottom insulating connector 16 is threaded on the core support rod 10 and the washer 40 is placed adjacent the inner end of the insulating connector 16 and silver soldered to the core support 10 thus serving as an electrical connection between the coil and core support rod 10, as will be apparent later. The sleeve 36 is placed about the core support and the bottom connector 16, as shown, with the top connector 18 left off. A magnetic material 38 is then placed between the sleeve 36 and core support rod 16) and above the washer 40 and tamped to avoid open spaces. Suflicient material is used to avoid any open space between the washer 40 at the bottom and the top connector 18 when these elements are secured to the core support 10, as shown. The material may be any magnetic material, for example, ferrite or other ferro-magnetic materials and may be in powdered, granular, tubular, rolled or other form. Also, depending upon the frequencies desired, the material may either be conductive or nonconductive. The insulator connector 18 is then screwed onto the threaded portion 14 of the core support 10.

Turning now to Figure 2, resin is injected into the space between the sleeve 36 and core 19 and impregnates the magnetic material 33. Any self-hardening or thermosetting resin which sets or is cured to a strong, tough, hard mass may be used, for example, any of the polyethylene resins. One suitable resin is sold commercially as Epon.

from'the bottom, the assembly being held in an inverted vertical position until resin comes out the space between the top of the sleeve 36 and the connector 16. In this manner the liquid resin rises evenly on all sides and carries the air ahead of it thereby avoiding air spaces in the resin when set.

For injecting the resin in this manner, a gun 40 is used which includes the piston 42 movable in the piston cylinder 44 which contains the resin 46. A projection 48 is provided on the cylinder 44 and includes a cylindrical opening 50 which snugly fits about the connector 18 and sleeve 36. An annular opening 52 is provided in communication with the interior of the cylinder 46 so as the piston is moved inwardly, resin is forced evenly into the space between the lower portion of the sleeve 36 and diameter portion 34 of the connector 18. Suitable packing rings 54 are provided on each side of the annular passage 52 for packing off this opening.

The gun 40 is satisfactory in use, although any suitable means or manner may be employed for injecting the resin and impregnating the magnetic particles.

When the resin comes out of the space at the top between the reduced diameter portion 32 of the connector 16 and the sleeve 36, injection is stopped and the gun removed. The resin is then allowed to set, or in the case of thermosetting resins is cured by heating.

After the resin has hardened, the sleeve 36 is removed, and as shown in Figure 3, the assembly is inverted and a coil winding 56 is wound about the resin impregnated with magnetic particles which is designated generally by the reference numeral 58. One end of the coil 56 is connected to the washer 40 thus completing an electrical connection with the core support which has the electrical lead 60 connected thereto, such as by silver soldering, so that electrical energy is provided from the lead 60 through the core support rod 10 to the washer 4t) and to the coil 56. A ground ring 62 is provided about the other end of the core support rod 11) and insulator 18 to which the other end of the coil 56 is connected, such as by silver soldering, and is grounded due to its engagement with the sub 31 which is screwed onto the threaded portion 26 of the insulator connector 18. As previously mentioned, a sub 29 is also threaded onto the threaded portion 24 of the insulated connector 16.

In use, if desired, a covering may be placed about the coil 56. It should be noted that the coil and coil core are supported at the thickest portion of the core support 14} and that the threaded sections of the subs 29 and 31 overlap a considerable distance with the threaded ends of the core support rod 1% through the medium of the insulators 16 and 18. The length of the threaded sections 24- and 26 is enough to provide shear strength approximately equal to the tensile strength of the threaded ends 12 and 14 of the core support rod 10.

The finished coil assembly possesses desirable electrical properties and at the same time has sufficient tensile strength to withstand shock, bending, torsion and extreme compressive forces encountered in use in well bores. Vulnerable electrical connections have been eliminated so that the coil assembly withstands extreme pressures without failure. The coil core support serves the dual function of being an electrical conductor and a structural member, and a tough, hard and durable coil core is provided which is so closely integrated with adjacent members that a coil wound about its surface is not'subjected to breakage due to external pressure. The coil assembly may thus be used successfully in well bores in investigating the conditions in well bores, for example, locating casing collars, stuck points of pipe and the like.

The present invention therefore is well suited to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein.

While only a presently-preferred example of the invention has been given for the purpose of disclosure, many changes in detail, steps of construction and arrangements of parts may be made which are encompassed within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. A coil assembly comprising, a core support rod having elongate reduced-diameter threaded portions at each end and serving as an electrical conductor, a coil core comprised of a resin impregnated with magnetic material disposed about the sup-port rod between the reduced diameter threaded portions, a washer secured about the core supportrod and serving as an electrical connec-v tion therewith, a pair of insulator connectors having internally and externally threaded portions, one each threaded to each reduced-diameter threaded portion, one abutting an end of the coil core and the other abutting the washer, a ground sleeve secured about the insulator connector abutting the coil core, a coil wound about the coil core and having one end electrically connected to the washer and the other end electrically connected to the ground sleeve, and a coil lead electrically connected internally to the core support rod, the externally threaded portion of the insulators adapted to receive threaded portions of subs substantially along their lengths so that the subs overlap the threaded portions of the coil support rod a substantial distance.

2. A coil assembly for use in a well bore comprising, a core support rod having elongate connecting portions at each end and serving as an electrical conductor, a coil core comprised of a resin impregnated with magnetic material disposed about the support rod between the connecting portions, a washer secured about the core support rod and serving as an electrical connection therewith, a pair of insulator connectors, one each connected to each connecting portions of the support rod, one connector abutting an end of the coil core and the other abutting the washer, external threads on said insulator connectors, a ground sleeve secured about one of the insulator connectors, a coil wound about the core and having one end electrically connected to the said washer and the other end electrically connected to the ground sleeve, and a coil lead wire electrically connected internally to the core support rod, the external threads on said insulators adapted to receive threaded portions of subs for support of the coil assembly in a well bore.

References (Iited in the file of this patent UNlTED STATES PATENTS 1,669,665 Karcher May 15, 1928 1,792,756 Osnos Feb. 17, 1931 1,869,878 Austin Aug. 2, 1932 FOREIGN PATENTS 445,998 Great Britain Apr. 22, 1936 

